The present invention relates to personal safety inhalation equipment, particularly breathing mask filters or respirators. More particularly, the present invention relates to an improved filter assembly with built-in seal check mechanism configured to enable rapid, effective negative pressure safety seal checks.
Negative pressure user seal checks are normally performed on personal air respirators by blocking the inlet portion of the filter cartridge and withdrawing air from the mask apparatus. A tight seal stops incoming air from leaking past the mask, creating a clearly detectable vacuum effect. A leaky seal results in a limited vacuum effect and a continuing flow of air into the mask.
To accomplish this test, the main air passage is blocked off, as with a separate structure such as a flat piece of cardboard or plastic applied against the outer surface of the filter, or by covering the inlet of the filter with the palm(s) of the user""s hand(s), and the user inhales as deeply as necessary to effect a collapsing of the respirator mask, due to the vacuum, which signals a good fit. The user""s thumbs may also be used to block the main air passage; however, the diameter of the apertures to be covered is normally larger than most user thumbs, providing a less-than-perfect seal for this very important personal safety equipment check.
However, problems arise from the difficulty in preventing air flow into the mask. These problems may arise from the imperfect seal effected by the cardboard or plastic, or the inability to use one""s hands to accomplish an effective seal. The latter often happens when the hands are dirty or gloves are worn.
An improvement (see FIG. 3) to this method is known in which a cover 100 having a small aperture 102 is snap-fit into place over a cartridge 104. However, the free airflow cross-sectional area of aperture 102 may in some instances be smaller than the free airflow cross-sectional area of cartridge 104, so it may become desirable to remove cover 102 from cartridge 104 for use. This action may disturb the fit of the mask, occasionally necessitating a repeat of the mask fit test procedure.